A three-point seatbelt system typically includes a guide or D-ring that is mounted to a structure of the vehicle. Seatbelt webbing of the three-point seatbelt system extends from a retractor and through a webbing slot of the D-ring. The seatbelt webbing slides on a guide surface of the D-ring as it passes through the webbing slot.
Tension in the seatbelt webbing applies a load to the D-ring. The D-ring transfers the load to the structure of the vehicle. For example, during a frontal vehicle crash condition in which an occupant of a seat is restrained by the seatbelt system, the retractor of the seatbelt system locks to prevent withdrawal of the seatbelt webbing. Due to inertia, the occupant tends to move forward relative to the seat. The forward movement of the occupant tensions the seatbelt webbing. The tensioned seatbelt webbing applies a load to the D-ring. The D-ring transfers the load to the structure of the vehicle.
The direction and magnitude of the load applied to the D-ring varies depending upon a variety of factors, such as crash conditions (e.g., speed and impact angle), the size of the occupant, and the location of the D-ring relative to the seat. Since the load may be applied to the D-ring in various directions, the D-ring may be pivotable relative to the structure of the vehicle. The pivoting movement of the D-ring helps maintain a position of the seatbelt webbing relative to the guide surface of the D-ring.
Seatbelt webbing, when viewed in section, preferably extends flat across the surface of the D-ring upon which it slides. When extending flat across the surface, the seatbelt webbing is evenly loaded across its width and distributes the load evenly along the surface of the D-ring. Seatbelt webbing passing through a D-ring may, however, experience a phenomenon known as “dumping.” Dumping is the bunching together of the seatbelt webbing at one end of the webbing slot. When dumping occurs, the seatbelt webbing may be loaded unevenly. The dumped seatbelt webbing concentrates the load on a particular portion of the D-ring.
The tendency of the seatbelt webbing to dump increases as the load exerted by the webbing on the D-ring increases. Therefore, it may be desirable to provide a D-ring designed to help prevent dumping.